Attempts have been made in the past to prepare infusion bags with a thickened portion or pad through which a hypodermic needle may be inserted for the purpose of injecting a drug or other medication into the contents of the bag. Such entry pads have been made from relatively thick, resilient material, such as rubber. Resilient pads of this type are suggested in U.S. Pat. No. 2,704,075 to Cherkin and in British Pat. No. 1,579,065 to A/S Haustrup Plastic.
The pad should be capable of providing sufficient support to hold a needle in place so as not to puncture adjacent or opposing portions of the bag. The pad material also should seal against leakage both along the exterior of the needle during injection and after removal of the needle. Difficulties have been experienced in the past in securing such resilient pads to the thin-film plastic materials from which the bags are made.
Another problem is that of keeping the outer surface of the injection pad sterile when the pad is pierced by a hypodermic needle. Although various types of coverings have been suggested in the past to keep the surface of the pad sterile, these coverings have certain disadvantages. For example, a pressure sensitive adhesive strip may come loose as the adhesive ages and loses its effectiveness. Plastic coverings welded to the wall of the bag may be difficult to tear or otherwise remove without violating the sterility of the pad.
Although U.S. Pat. No. 3,343,541 to Bellamy suggests a tearable covering for the port of a parenteral container, the covering is made from a relatively thin tearable film. This thin tearable film must be attached both to a thicker pull strip and to the bag wall around the port area. Because the tearable film is relatively fragile, it is difficult to handle and to secure to both the pull strip and the bag wall. Furthermore, the resulting covering may be easily ruptured unintentionally during manufacture or subsequent handling of the bag, thereby contaminating the port area.
Due to difficulties in reopening a sealed plastic tube, infusion bags previously have been provided with multiple tubes in communication with the bag interior. For example, a bag may have separate tubes for filling, for emptying and for adding medications immediately prior to use. Such multiple tube arrangements are expensive to manufacture and increase the likelihood of an inadvertently broken connection.